Hydrofoil boat



May 25, 1965 J. BADER 7 3,185,120

HYDROFOIL BOAT Filed July 30, 1964 3 Sheets-Sheet 1 FIG. I. INVENTOR.

JOHN BADER E :1 ATTY.

AGENT J. BADER HYDROFOIL BOAT May 25, 1965 3 Sheets-Sheet 2 Filed July30, 1964 lOl FOIL BORNE WATERLINE FIG. 2.

JOH/V BAUER J. BADER HYDROFOIL BOAT May 25, 1965 Filed Jul so, 1964 3Sheets-Sheet 3 FIG. 4.

INVENTOR.

JOHN BADER United States Patent 3,185,120 HYDROFOE BOAT John Baden,Montgomery County, Md. (4513 Sangamore Road (Apt. 101), Washington,D.C.) Filed July 30, 1964, Ser. No. 386,466 15 Claims. (Cl. 11466.5)(Granted under Title 35, US. Code (1952), sec. 266) The inventiondescribed herein may be manufactured and used by or for the Governmentof the United States of America for governmental purposes without thepayment of any royalties thereon or therefor.

This invention relates to hydrofoil craft and more particularly, toimproved hydrofoil retraction means by which symmetrically mountedprimary lifting foils supporting most of the craft may be extended to alocked surfacepiercing position of rigid support and by which the foilmay be retracted to a compact stowed position located alongside the hullin a dry position essentially above the crafts displacement waterline. Afeature of the hydrofoil craft of the present invention is a novelhydrofoil mounting arrangement for the outboard unit of aninboard-outboard power plant employed on the improved craft.

In overcoming the difliculties basic to hydrofoil craft of rigidity ofsupport and of facility of retraction to a dry position withoutdetracting from stability, the novel retraction means provides in itsextended position a wide V-shaped hydrofoil support without reversedihedral positions which would lessen stability. The retraction meansitself is composed of a plurality of support members all of which arepivotable. When retracted, these members including the hydrofoils liesubstantially flush against the hull. When extended, these pivotablemembers form a plurality of triangular frames which insure rigidity ofthe hydrofoil against lift forces and impact loads, and which locateopposing hydrofoils on either side of the craft so that the lift forcesof the opposing hydrofoils converge to a point above the crafts centerof gravity. Because all of the support members are pivotable, only aminimum of small brackets are required to be afiixed to the hull tosupport the retraction means, consequently rendering the retractionmeans easily mountable on existing hulls without expensive and unsightlyhull alterations.

In further carrying out the invention, in View of the wide present dayacceptance of power plants of the inboard-outboard type, there isprovided for such powerplant in the hydrofoil craft of the presentinvention a surface-piercing, V-shaped hydrofoil which is advantageouslylocated on a lengthened surface-piercing propeller strut an appreciabledistance above the propeller so that, unlike previous known designs,there is no possibility that the propeller can be lifted out of thewater by the hydro foil at flying speeds. Together with the foregoingadvantageous arrangement there is further provided additional supportmeans for strengthening the outboard unit of the powerplant to transmitto the hull the lift forces produced by the propeller strut hydrofoil.Since such lift forces are transmitted to the hull, the strut hydro foilprovides the additional advantage of stabilizing the hull attitude inits water-displacement made by lifting the stern to prevent porpoisingor squatting.

It is, then, among the objects of the present invention to provide: animproved hydrofoil craft of the type employing inboard-outboardpowerplants including improved primary retractable hydrofoil means andadditional hydrofoil means for the support of the aft portion of thehull through the outboard unit of the powerplant; improved hydrofoilretraction means composed entirely of easily movable pivotable supportmembers extendable to a rigid, locked position; an improved hydrofoilcraft having a unique arrangement of pivotally mounted support memberswhich can be separately fabricated and attached to a hull in a simplemanner; an improved hydrofoil craft to the hull of which is attached aset of surfacepiercing hydrofoils which can be retracted simply andeasily into a compact, dry stowage position alongside the hull; animproved hydrofoil craft having a minimum number and size of hullappendages to which hydrofoil retraction means may be attached and bywhich the retraction means may be easily moved to an active extendedposition and to a passive, stowed position and from which the retractionmeans may, if desired, be easily removed; and, in a hydrofoil craftimproved aft-supporting hydrofoil and mounting means for a powerplant ofthe type having an extended surface-piercing strut whereby the dynamicriding qualities of the craft are enhanced both in the flying and waterdisplacing modes.

It is a feature of the present invention to provide novel means forstrengthening the support of known types of inboard-outboar powerplantsso that they may be fitted with hydrofoil means according to theinvention. It is typical of the known types of inboard-outboardpowerplants that the surface-piercing propeller struts are rotatableabout a vertical axis for steering and about a horizontal axis forwithdrawal or shock load yielding of the outboard unit of thepowerplant. However, the usual design of these rotational axes is onlysufficiently strong to resist the forward thrust of the propeller. Inview of the fact that a hydrofoil positioned on the strut in accordancewith the present invention produces a vertical lift force of about threetimes the thrust force of the propeller, it is necessary to provide inaccordance with the invention additional clamping and load transfermembers arranged in a novel manner to compensate for the additionalhydrofoil lift without disturbing the rotational axes of the powerplantsas designed.

A better understanding of the above and other features of the presentinvention will be obtained by reference to the following detaileddescription and accompanying drawings throughout which like numeralsrepresent like parts and in which:

FIG. 1 is a modified transverse cross sectional View of a hydrofoilcraft according to the invention depicting the spectively the extendedand retracted positions of the primary hydrofoil; and

FIGS. 2 and 3 are views in side elevation depicting respectively theextended and retracted positions of the primary hydrofoil;

FIGS. 4 and 5 taken together are respectively side elevation and endviews also showing certain details in cross section, of the outboardunit of the powerplant according to the invention.

Referring to FIGS. 1-3 taken together, there is shown therein a boat 11having a V bottom 13 extending from a keel 15 and joined to a side 17 ata chine 19. The side 17 is joined to the deck 21 at a gunwale 23. Thehydrofoil retraction means for a hydrofoil on either side of the craftwill now be described as oriented in its extended position shown insolid lines in FIG. 1 and in FIG. 3.

A pair of brackets 25 supporting a hinge 27 are located forward of theboats center of gravity adjacent the gunwale 23 on the side 17. Thehinge 27 is oriented approximately parallel to the gunwale. The hinge 27supports the upper end of an upper link 29. The lower end of the upperlink carries a transverse hinge 31 of any suitable construction to whichis attached the upper end of a strut 33 so that the strut swings freelyabout the hinge 31 in a transverse plane.

The lower end of the strut 33 has a hinge 35 to which is attached thecorner portion of a dihedral type hydrofoil 39. The hydrofoil 39 has aninwardly projecting foil portion 41 which is oriented to ride in a planeapproximately parallel to the water surface, and an outwardly extending,surface-piercing foil portion 43 which as best seen in FIG. 3 is sweptback as it extends outwardly.

Near the sweptback extremity of the foil portion 43, which rides abovethe water surface, is a bracket mounted hinge 45 to which is attachedthe outer end of a brace 47. The inner end of the brace 47 is attachedto a bracket mounted hinge 49 located in the same transverse plane asthe hinge 45 andrnounted along the chine 19. The brace 47 may be furtherheld against fore and aft movement by a strut 51 swivelly attached atits forward end to the aft portion of the brace and attached at itsafter end to the hinge 49 for rotation therewith. This added fore andaft support may be desirable where considerable forces are expected,such as, in very high speed operation. If desired, the brace 47 may beswept forward.

. The strut 33 is provided with transverse support by a lower link 53the upper end of which is attached to a bracket-mounted hinge 55extending along and adjacent to the chine 19, and hingeably attached atits lower end to the hinge 57 located on the lower central portion ofthe strut 33. The lower link 53, upper portion of the strut 33 and theside 17 together form a triangular or A frame element for supporting thehydrofoil in the transverse.

plane.

In order to hold the strut 33 in place against transverse movementcaused primarily by hydrofoil lift forces during turns, there isprovided a clamp 59 mounted on the side 17 a short distance below thegunwale 23. The clamp 59 is composed of a pair of brackets for holding arod 61 against the outer surface of the upper link 29 so that the upperlink is held in place preventing movement of the strut 33 and lower link53 in a transverse plane.

If desired, additional fore and aft support for the strut 33 is providedby a support member 63; shown in FIGS. 2 and 3, one end of which isrotatably mounted on the hinge 55 aft of lower link 53 and the other endof which is swivelly attached to the lower link 53. Of course, all ofthe hinges are parallel to each other.

The retractable hydrofoil means just described may be retracted by anysuitable means, such as by hand, power operated means of knownconstruction, and remote control power means. The act of retracting thehydrofoil and the accompanying movements of the retraction apparatuswill now be described with particular reference to FIG. 1. First, therod 61 in the clamp 59 is removed. The upper link 29 is then rotatedabout hinge 25. When the lower end of the upper link 29 has reachedposition A, the lower end of the strut 33 has been moved slightlydownwardly and inwardly to its'A position due to a small relativepivoting motion of the strut 33 about the hinge 57 at the lower end ofthe lower link 53 as link 53 is pulled outward by the strut to its Aposition. Consequently the hinge 45 at the extremity of the brace 47drops slightly to its position A, and the hydrofoil 39 has movedslightly inwardly to its A position with strut 33.

As the upper link 29 is rotated further to its B position, which can beobserved to be higher than its A position, the strut 33 is pulledupward, its upper end rotating about hinge 31 and its lower end arrivingat position Bf-almost directly above the original extended position ofhinge 37. The hydrofoil 39 has also reached its position B which is justabove it original position.

Before proceeding further, it is noted that the initial reverse movementof the hydrofoil 39 and associated linkage to position A provides anadditional locking bias against outward forces when the hydrofoil isfully extended. This locking bias further inhibits collapse of theretraction system on sharp turns where outward acting forces are at amaximum on either the starboard or port side of the boat.

Continuing with the retraction, upper link 29 is further rotated abouthinge 25 so that its extremity at hinge 31 reaches position C. Hinge 35at the bottom of the strut 33 therefore travels generally upwardly toits position C,

pulling along with it the hydrofoil 39 and the brace 47. Thus, while thestruit 33 is generally moved in translation, the brace 47 is rotatingabout fixed hinge 49 along with its support 51 and the hydrofoil 39 ismoving in both translation and rotation so that the hinge 45, brace 47and the hydrofoil 39 has reached its C position.

The upper link 29 is rotated so that the hinge 31 comes to rest at theposition of full retraction, D. As best shown in FIG. 3, in theretracted position the upper link 29 protrudes for approximately its ownlength above the deck 21; the strut 33 has been moved primarily intranslation so that it is drawn flush against the side 17 with its upperend protruding above decks coextensively with the upper link 29. Thebrace 47 has been rotated about hinge 49 so that it rests flush againstthe side 17. The hydrofoil 39 has been moved primarily in translation sothat it overlies the strut 33 and the top of brace 47 adjacent the side17 in a swept back fashion with its inner foil element 41 restingadjacent the V bottom 13. The lower link 53 has been rotated about thehinge 55 so that it rests against the side 17.

The hydrofoil may be locked in its retracted position by any suitablemeans which, by way of illustration only, may be a clamp located on theside 17 or by deck hardware of known construction. Of course, thehydrofoil may be lowered in a reverse manner to its retraction describedabove.

By way of illustration and not limitation, the various linkages in theprimary hydrofoil retraction means may have the exemplary relativedimensions shown in the following table, assuming the transverse lengthof the side 17 to have a length 2r:

Part Preferred imensions About I or slightly less.

About 2r to 3.5r.

- About 2r or greater.

About 2%r.

About optional r recommended.

Foil portion 41 Reference is now made to FIGS. 4 and 5 in which is shownan inboard-outboard powerplant modified in accordance with the inventionto carry a hydrofoil to provide, along with the primary foil 39, animproved hydrofoil craft.

7 More particularly, there is shown in FIGS. 4 and 5 components of aconventional inboard-outboard powerplant which includes a drive shaft 71with its tubular housing 73 extending thru the boats transom 75. Thedrive shaft 71 extends thru an outboard connect fitting usually in theform of a hollowed out casting 77 to an upper gear box 79 whichgenerally has co-acting bevel gears to transfer the drive shaft rotationto an intermediate drive shaft (not shown) extending thru a hollowfaired strut section 81 to a lower gear box 83. The housing 73 has atits aft end a flange 84 located externally of the transom.

The lower gear box 83 has beveled gears which coact to transfer therotation of the intermediate drive shaft to an output shaft 85 carryinga propeller.

Furthermore, the conventional inboard-outboard unit has a horizontal ortransverse pivot with its axis 86 extending thru the casting 77 so thatthe lower part of the unit may be lifted from the water, or may yielddue to shock loading on the lower part of the unit. A shear pin isusually provided in the lower part of the casting 77 to hold the unit inplace when underway. Of course, the drive shaft may be provided with auniversal joint (not shown) with an axis coaxial with the horizontalpivot axis 85. The gear box 79 is generally in the form of a castinghaving a shaft housing 87 terminating in a flange 89 at its lower end.The flange 89 is bolted to a flange 90 of like dimension located at theuppermost end of the hollow strut 81.

The housing 87 has at its forward portion and integral therewith anupper pad 91 having an aperture 93 and a pad 95 located below and spacedfrom the pad 91 having an aperture 97 coaxial with aperture 93. A pivotpin 99 is positioned in the apertures 93 and 97 and in correspondingapertures located in the flanges 9t), 91, so that the outboard portionof the unit may rotate about the pivot pin for steering the boat.

The forward part of the casting 77 also has a tubular extension 160which fits inside the housing 73 to hold the outboard unit in place.

In carrying out the present invention, the hollow, faired strut 81 islengthened. A V-shaped, surfacepiercing hydrofoil 101 which may beeither in line with or swept back from, the transverse plane of thestrut 81 is mounted on the strut an appreciable distance above the axisof the propeller shaft 85. The location of the hydrofoil above thepropeller shaft is significant because, contrary to prior arrangements,such a location insures that the hydrofoil will not be able to lift thepropeller out of the water. Of course, the use of a swept back hydrofoilhas the advantage of reducing shock loading on the hydrofoil and itssupporting elements.

As indicated in FIG. 4 by the three arrows X, Y and Z emanating fromorigin 0, the hydrofoil 191 produces a drag component X and a liftcomponent Y which together produce a resultant force Z which tends tocause via the lever arm action of the strut 81 great strain on thetubular extension 199 and also places considerable strain on the casting77 against shear pins usually provided to hold it in place. Thisresultant force Z may be of a value about three or more times as greatas the thrust of the propeller.

According to the invention the outboard unit is strengthened to acceptthe hydrofoil-produced forces first by inserting an annular bearingplate 193 of sturdy construction within the cupped flange 84. Theportion of the casting 77 adjacent the ring 1113 is strengthend byfinshaped weldments or integral webs 105 which welded or securelyfastened in any suitable manner to the annular bearing plate 1&3.

An inverted A frame 107 of sturdy construction is inserted within theopen end of the casting 77 so that its lower crossmember 1% is securedto the pad 95. The upper and lower cross members 108a and 108respectively, of the A frame 167 are apertured to receive the pivot pin99. The bottom of the casting 77, the pad 95 and the lower end of the Aframe are provided on both sides with lateral apertures 1439 forreceiving shear pins 111. The upper end of the A frame 197 is secured byany suitable means to the pivot at horizontal axis 85. Thus, the A framevia the shear pins 111 and its upper mounting at axis 85 takes up someof the forces which would otherwise be transmitted to the transom solelyvia the casting 77 and thus serves to reinforce the casting 77.

In order to provide for transmission of forces to the A frame and thenceto the transom, a pair of canted braces 113 located on either side ofthe casting 77 are at their lower ends welded to the flange S9 and attheir uppermost ends to the upper pad 91.

Therefore, responsive to the Z forces tending to rotate the strut andoutboard unit about the plate 84 (because the pivot at axis 85 islocated by shear pins 111), such forces are transmitted principally viathe strut flange 9t flange 39, braces 113, A frame 197 and pin 97, websor weldrnents 84 to the annular bearing plate 103, thus alleviating theconventional outboard unit from strains which would otherwise besubjected to the hydrofoil-produced forces.

The attitude of the hydrofoil 191 and the attack angle of the propellermay be adjusted by changing the location of the shear pins 111 inapertures 199. As a guideline,

6 but not by way of limitation, the primary hydrofoil 39 may provideabout 75% of the lift while the aft hydrofoil 101 provides the remaining25% of the lift.

The aft V-shaped hyrofoil 101 not only provides lift in the flying modeof the craft, but further provides a rudder effect to facilitatesteering. There is also provided a stabilizing effect to minimizeporpoising in the water-displacing mode because the hydrofoil 101 willtend to cause the stern to move up and the bow to move down.

It is appreciated that due to the fact that the various elements of theprimary hydrofoil retraction means is composed of hinged parts, it maybe easily fabricated and supplied to users in easily assembled kit form.Of course, the sizes and proportions of the various elements depend uponthe size and displacement of the craft to be supported thereby, and theelements may be supplied to users in sets appropriate to the dimensionsand displacement of the craft. Obviously, any suitable materials may beused for the elements, such as, for example, structural metals andalloys thereof, plastics such as fiberglass or the like, and wood. It isappreciated that especially where metals are used, the fact thataccording to the invention the hydrofoil unit retracts to an essentiallydry position inhibits corrosion, erosion and deterioration of thehydrofoil material.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. An improved hydrofoil craft having sides and a bottom, said crafthaving surface piercing strut means supporting propeller means,comprising:

at least one primary hydrofoil unit having separate hydrofoil elementslocated symmetrically about and displaced transversely outward of thecenterline of the craft, said hydrofoil unit being mounted forwardly onthe craft;

retraction means for said hydrofoil elements;

said retraction means comprising a plurality of support elementshingeably mounted on the external sides of the craft and connected tothe hydrofoil element;

said support elements when extended forming with the side a plurality ofrigid triangular braces connecting the hydrofoil element to the sides;

said support elements being collapsible by relative rotation thereofabout the respective hinged interconnections to raised positionsessentially flush alongside the sides of the craft and essentially abovethe displacement water line of the hull;

a secondary hydrofoil unit including foil means mounted on the propellerstrut means an appreciable distance above the propeller means.

2. Apparatus according to claim 1 wherein the secondary hydrofoil unitcomprises surfacepiercing V-shaped hydrofoil means.

3. Apparatus according to claim 2 wherein said plurality of supportelements comprises:

upper and lower spaced links each mounted on the side of the hull forrotation about one end in essentially one transverse plane;

a strut supported by the other end of both said links, the upper end ofsaid strut being pivotally connected to the other end of the upper linkand the strut pivotally connected in its central portion to the otherend of the lower link;

means pivotally connecting the lower end of said strut to an inboardportion of the hydrofoil element, and a brace mounted to the hull at itsinner end and at its other end to the outer end portion of the hydrofoilelement; and means locking said upper link in a downward extendingposition alongside the hull, whereby the hydro- 7 foil element is lockedin an operating position by said lower link, strut and brace, said upperlink when rotated to a raised position causing movement of the lowerlink, strut, hydrofoil and brace to a raised position alongside thehull.

4. Apparatus according to claim 3 including additional support means forsaid brace and for said lower link for further locking the hydrofoilelements against fore and aft movement.

5. Apparatus according to claim 3 wherein the retraction means ischaracterized by the ratio of the length of the lower link to the strutupper link, brace and hydrofoil being of respective values such thatduring a large portion of the extension of the retraction means thehydrofoil moves in rotation and translation in a first directional senseand in a second essentially opposite directional sense for a smalldistance of extension into its locked down position.

6. Apparatus according to claim 5 wherein said ratios are characterizedby the following respective values, said lower link having a length rilower link to strut, r to approximately 2.8r; lower link to brace, r toapproximately 2.2r; lower link to hydrofoil, r to approximately 2.6r,and lower link to upper link, r to approximately r.

7. Apparatus according to claim 6 wherein the length of the side ofthecraft in transverse cross section at the approximate plane of retractionis at least 2r.

8. Retraction means for each surface-piercing, swept back hydrofoil of awater craft having sides and a bottom, and supported by a symmetricalarray of hydrofoils, each hydrofoil being mounted as a separate unit onone side of the craft, comprising:

upper and lower links;

means rotatably mounting the one end of the upper link at the upperportion of the side and one end of the lower link directly below theupper link approximately at the junction of the side and bottom;

said upper and lower links being of dimensions so that their other endsmay rotate in the same transverse plane of the watercraft free of eachother;

a strut rotatably attached at its upper end to the other end of theupper link and rotatably attached in the vicinity of its central portionto the other end of the lower link;

said strut being of a length at least greater than the combined lengthof said links;

means rotatably attaching the submergible portion of thesurface-piercing hydrofoil element to the lower end of said strut;

a brace rotatably attached at one end to a lower portion of the side ofthe craft and at its other end to the swept back above-surface portionof the hydrofoil;

the hull attachment point of said brace being located in a placedifferent from said transverse plane; and

means for holding the upper link in position against the side wherebythe retraction means is held in an ex tended position, the hydrofoilthereby being held in a rigid surface-piercing position by virtue oftransverse frames constituting in one instance a portion of the side,said lower link and said strut and in another instance said brace,hydrofoil and strut, and in another plane, constituting said brace,hydrofoil and a fore and aft distance along the side;

said retraction means when drawn up lying essentially flush alongsideand above the water displacement line of the water craft.

9. Retraction means according to claim 8 but further characterized byadditional fore and aft support means rotatably attached to said lowerlink and to said brace.

10. Retraction means according to claim 9 wherein each of said links hasa length r, the length of the brace is approximately 2.2r, the length ofthe strut is approximately 2.8r and the length of the hydrofoil isapproxis mately 2.6r;

said lower link being connected to said strut at a 8 locationapproximately a distance r above the connection point of the strut tothe hydrofoil, whereby during most of the extension of the retractionmeans the hydrofoil moves in rotation and translation in a firstdirectional sense and during its final brief movement into fullextension moves in a directional sense essentially opposite to saidfirst directional sense thereby establishing a locking bias for thehydrofoil.

ll. Retraction means for each one of a plurality of surface-piercinghydrofoils symmetrically arranged on a watercraft having sides and abottom, comprising:

a first plurality of support members each rotatably attached at one endto respectively different portions on the side;

a second plurality of support members each rotatably attached at one endto different portions of the hydrofoil;

means rotatably connecting the other end of one of said second pluralityof support members to the other end of one of said first plurality ofsupport members;

means rotatably connecting an intermediate portion of said one of saidsecond plurality of support members to the other end of another of saidfirst plurality of support members, and means rotatably connecting oneof said first plurality of support members to an above-surface portionof the hydrofoil whereby the hydrofoil is extendable to a positionsupported by triangular elements formed by said support members and isretractable to an alongside position in which said support members areoverlyingly collapsed.

l2. Retraction apparatus fora hydrofoil craft having sides and a bottomand having hydrofoil elements mounted as single units on both sides ofthe craft symmetrically about the crafts centerline axis, the retractionapparatus for each hydrofoil element comprising:

an upper link rotatably mounted at one end at the approximate top of theside and a lower link having one end rotatably mounted at theapproximate bottom of the side;

each of said links being rotatably in essentially the same transverseplane and in paths free of each other;

a strut at least longer than the combined length of said links androtatably attached at its uppermost end to the other end of said upperlink and rotatably attached at a point approximately near its lower endto the other end of said lower link;

said strut being rotatably attached at its lowermost end to the inboardportion of the hydrofoil element;

a brace rotatably attached at one end to the side for rotation about anaxis which is at least approximately coaxial with the rotational axis ofsaid lower link;

the other end of said brace being rotatably attached to a point near theouter end of the hydrofoil element;

the length of the brace being less than that of said strut whereby whenthe unit is extended, the hydrofoil element is located in asurface-piercing attitude;

said hydrofoil element being of a length at its points of connection tothe strut and brace at least greater than the length of the brace;

whereby in the extended position essentially rigid hydrofoilelement-supporting triangular elements are formed by the lower link,craft side and strut and further by the brace, hydrofoil andlongitudinalportion of the side;

and further, whereby upon retraction said strut and hydrofoil are bothrotated and translated due to relative rotation of the links about therotatable attachments on said strut and due to relative rotation of thestrut and brace about their respective and rotatable attachmcnt pointson the hydrofoil element;

thereby raising all of the members to positions overlying each otherwith the foil outermost essentially alongside the side coextending tothe juncture of the side and bottom.

13. Apparatus according to claim 12 wherein said hy- 9 drofoil elementis swept back from submergible inboard portion toward its above-wateraftward portion, the point of rotation of said brace being aft of therotational axis of said lower link.

14. Apparatus according to claim 13 but further including clamp meansattachable to the side for holding the upper link in a down positionalongside the side, whereby the unit when extended is further locked ina position wherein the members form triangular support elements.

15. An improved hydrofoil craft having sides and a bottom, said crafthaving a propulsion unit including an inboard powerplant and an outboarddrive unit extending from the powerplant thru the crafts transom, saidoutboard drive unit having a drive shaft housed in a surfacepiercingstrut extending downward to a propeller shaft, and wherein the outboardunit is of the type supported essentially by a sleeve bearing against atube passing thru the crafts transom, said tube having an exteriorcupped flange portion, said outboard unit having an aftwardopeningshell-like fitting for holding horizontal axis pivot means for saidoutboard unit, said fitting being integral with the sleeve, and a gearbox housing with upper and lower spaced pads extending into the fittingfor holding a steering pin, and further, said gear box terminating atits lower end in a flange and the surface-piercing strut terminating atits upper end in a flange abutting said gear box flange, said craftcomprising:

retractable hydrofoil means located essentially forwardly of the craftfor carrying a primary portion of the crafts weight when the craft isflying;

aft hydrofoil means located on the surface-piercing strut for producinglift for the after portion craft in both its water displacing and flyingmodes;

said surface-piercing hydrofoil being located at least appreciably abovethe axis of propeller rotation; and

Cir

means additionally supporting the outboard unit against the lift forcesproduced by said aft hydrofoil means, said means comprising:

an inverted A frame member resting on the lower pad of said gear boxhousing with its cross member supported by the upper pad and its endssupported by the horizontal axis pivot means;

a pair of forwardly and upwardly canted braces connecting the gear boxflange with the upper pad; and

a bearing support ring located in said cupped flange and welded to theforward portion of the shell-like fitting, said shell-like fitting beingheld against the gear box housing by shear pin means acting via saidinverted A frame;

whereby the resultant of the lift and drag forces acting on saidoutboard unit are transmitted via said braces and A frame stilfenedfitting for strain reaction on said bearing support ring.

References Cited by the Examiner UNITED STATES PATENTS 2,887,979 5/59'Bader 114--66.5 2,955,559 10/ Palmer et al. 114-66.5 2,984,197 5/61Bader 11466.5 2,991,747 7/61 Badder et al 114-665 3,081,728 3/63Wilterdink et a1 11466.5 3,088,296 5/63 Barker et al 41 3,099,239 7/ 63Von Schertel et al 114-665 FOREIGN PATENTS 1,066,897 10/59 Germany.

0 FERGUS S. MIDDLETON, Primary Examiner.

1. AN IMPROVED DHDROFOIL CRAFT HAVING SIDES AND A BOTTOM, SAID CRAFTHAVING SURFACE PIERCING STRUT MEANS SUPPORTING PROPELLER MEANS,COMPRISING: AT LEAST ONE PRIMARY HYDROFOIL UNIT HAVING SEPARATEHYDROFOIL ELEMENTS LOCATED SYMMETRICALLY ABOUT AND DISPLACEDTRANSVERSELY OUTWARDLY OF THE CENTERLINE OF THE CRAFT, SAID HYDROFOILUNIT BEING MOUNTED FORWARDLY ON THE CRAFT; RETRACTION MEANS FOR SAIDHYDROFOIL ELEMENTS; SAID RETRACTION MEANS COMPRISING A PLURALITY OFSUPPORT ELEMENTS HINGEABLY MOUNTED ON THE EXTERNAL SIDES OF THE CRAFTAND CONNECTED TO THE HYDROFOIL ELEMENT; SAID SUPPORT ELEMENTS WHENEXTENDED FORMING WITH THE SIDE OF PLURALITY OF RIGID TRIANGULAR BRACESCONNECTING THE HYDROFOIL ELEMENT TO THE SIDES; SAID SUPPORT ELEMENTSBEING COLLAPSIBLE BY RELATIVE RO-